Wednesday, February 7, 2018

Digest for comp.programming.threads@googlegroups.com - 2 updates in 2 topics

pvr.ram34@gmail.com: Feb 06 12:32PM -0800

https://unacademy.com/course/concepts-of-c/38RLD30R
Steve Watt <steve.removethis@Watt.COM>: Feb 06 12:23AM

In article <8aa2d575-75b9-4bbd-aa75-4dc9605931d2@googlegroups.com>,
<gee.akyol@gmail.com> wrote:
[ ... ]
>at a time, it is easy to do. If it is required that "dead" threads be also
>detected when readers are involved, a list of readers have to be maintained.
 
>So make sure you crash only when u have the write lock & not the read lock :-)
 
And make sure you crash only when you're leaving the data structure in a
state that won't nuke other accessors. But the owning thread crashed,
so it's a huge gamble about whether the protected data structure is
safe.
 
Having a shared lock silently succeed when the previous write-locking
owner dies is a terrible idea. EOWNERDEAD exists to allow code that can
do sanity checks or reconstruction on data structures.
 
Basically what will happen with your scheme is that some thread will
take the write lock, start manipulating the data structure, and explode
while pointers are still in an inconsistent state. Then the next (more
innocent) thread will come along, attempt to modify the data structure
in some other way, and also crash. Lather, rinse, repeat, until all
processes that might update the shared structure have crashed.
 
Good luck debugging the mess that ensues.
--
Steve Watt KD6GGD PP-ASEL-IA ICBM: 121W 56' 57.5" / 37N 20' 15.3"
Internet: steve @ Watt.COM Whois: SW32-ARIN
Free time? There's no such thing. It just comes in varying prices...
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